Some more progress, some more information. I'm taking the time to post this so maybe it will help someone else some day.
I remembered why I didn't use the Dell...no onboard parallel port. The addon card I had was not recognized by Ubuntu 10.04 and I could not find drivers for it.
Next up was the HP P4 I mentioned in my last post. HP a1320y, as I recall, P4 D 3Ghz, 1.5 GB RAM. What a colossal failure. First, the system hung on bootup (POST, not Ubuntu) with my kick-butt Gigabyte video card. Hmm, okay, back to the factory onboard card. I had a SATA drive in the system. Loaded the Live CD with U10.04. Latency from HELL. Servo thread was showing numbers in the 600,000 range and up almost immediately whether I ran the test immediately after bootup or half an hour after bootup. Actually doing things like opening Firefox and moving windows on screen gave me over 700,000 for servo thread and, regardless of usage, I got over 300,000 for base thread. Attempting to disable SMI (System Management Interrupt or whatever) did not work.

F* F* F*
Hmm. Okay, I was using the same HD from the other problem-child I'd originally posted about. I grabbed a EIDE WD 40GB 7200 RPM disk I had laying around and tried that. It was magical. My servo thread jumped to over 1,000,000...with some results over 2,000,000 and higher base thread numbers, too. Not a happy camper.
I read about the SMI problem and about it being included with some Intel chipsets. So, I decided, fine, I'll give Ubuntu and old PC and see what happens (maybe an older system wouldn't have the SMI on it).
I have a system that is about 8 years old I guess. P4 1.8 Ghz, single core. I had tried to mix-n-match RAM and had 1.75 (roughly) GB installed...1GB stick, 512MB stick, and a 256MB stick but that didn't work, the system only saw the 768MB. No biggie. Latency tests showed < 35,000 for the servo thread...even though it's running on a litter-mate WD 40 GB 7,200 RPM drive and on the onboard video. I shut the system down and removed the 512 and 256MB sticks and the system then used the 1GB stick. Latency times dropped a little more (maybe because the 1GB stick is PC3200 IIRC and the 768 combined sticks were PC133). Now running the test for 10 minutes+ showing servo thread latency of 32,405. MUCH improved over the HP with the dual core P4 and 1.5 GB RAM with a SATA drive (or the EIDE drive). Go figure that one out. :blink:
The motherboard in this old system is an ASUS P4S533-MX.
Latency on this system is: Servo 99,308 and Base 32,405.
EMC2 loads with no errors about latency or RTAI and Axis runs/loads fine.
So, I'm wondering...if the SMI stuff is only prevalent on Intel chipsets (and maybe I'm being ignorant of chipset manufacturers here), why couldn't I (we) try using a system based on an AMD processor? Do they use Intel chipsets? Sorry, lonnnnng time, no hardware monkeying.
I am considering just buying one of the Intel D510MO that BigJohnT has had good luck with. This stuff with Ubuntu/EMC2 was supposed to help me with a grassroots approach to CNC but it's being a pain with the hardware problems I've had.
Thanks to those who have helped me. I hope this will give a little back.
--HC